1. Field of the Invention
The present invention relates to a system and method for monitoring vital signs and capturing data from a patient remotely using radiotelemetry techniques. In particular, the present invention is a low cost, patient-friendly, ambulatory monitoring system for remote electronic capture of nonincasive vital signs data including, e.g., full waveform ECG, repiration rate, skin temperature, and blood pressure. The present invention also has the capability for real-time monitoring or recording of continuous or point-in-time information with the data presented to the user in a tailored form. Monitoring software included in the system of the invention may also incorporate full ECG analysis as well as alarms for arrhythmias and other abnormalities determined from the measured vital signs.
2. Description of the Prior Art
Before drugs and related therapies are approved for widespread use by physicians, such drugs and therapies typically undergo numerous trials for efficacy and safety. Successful human trials are critical to regulatory approval of a new drug or therapy, and accordingly, much money an effort goes into the human trials. At present, patients are selected for the trial and placed on the regimen under test. The efficacy and safety of the drug and/or therapy is tested by having the patient make numerous visits to his or her physician for testing during the trial period. While a great deal of information can be gathered at such tests, generally there is no method for collecting the data between physician visits, thereby causing decisions regarding efficacy and safety to be made based on a small sampling of the patients"" experiences with the drug and/or therapy. More frequent visits to the physician would improve the data pool; unfortunately, such visits are expensive, add to the overall cost of the trial, and, because a limited data set is available, the trial duration is lengthened, thereby delaying the drug""s market introduction.
An improved technique for testing the efficacy and safety of a drug and/or therapy is desired which does not require additional visits to the physician. It is desired to develop a technique for collecting data from a human subject at all times during a trial without requiring any visits to the physician""s office, thereby eliminating the cost and inconvenience of visiting the physician""s office for routine monitoring.
Also, an improved remote patient monitoring/management system is generally desired whereby useful vital signs data may be obtained from a patient without requiring frequent visits to the physician""s office. Such remote monitoring/management is particularly desirable for home patient monitoring of patients with chronic illnesses such as congestive heart failure of for post-operative or out-patient monitoring. Prior art patient telemetry systems have had limited commercial success for a variety of reasons such as difficult of use and cost.
Remote patient monitoring techniques are generally known in which electrodes are placed on the patient to monitor the patient""s vital signs and the captured data is transmitted to a remote display for monitoring the patient""s condition. Remote monitoring systems are known which permit a doctor or nurse to monitor the conditions of several hospitalized patients from a central monitoring site in the hospital. Typically, sophisticated patient monitoring equipment is used to collect data from the patient, and the collected data is transmitted via wire to the central monitoring site in the hospital. Generally, wireless systems are problematic in the hospital setting because of the proximity of the respective patients and the amount of interference found in such a setting.
Typically, most of the patients receiving a particular drug regimen or therapy being tested are ambulatory and, in many cases, participating in the study from home. Remote monitoring of patients from their homes introduces an entirely new set of challenges for transmitting the gathered data to a central location for evaluation. Numerous attempts have been made to facilitate such data collection and trasmission; however, in each case, cumbersome and uncomfortable monitoring equipment is placed on the patient and the patient is tethered to the monitoring equipment by electrical cords, thereby limiting the patient""s movement. In some prior art systems, the electrical cords have been removed and the transmissions to the monitoring equipment made using telemetry techniques; however, such systems have been used primarily for real-time vital signs monitoring and not for data collection of the type needed for diagnosis and efficacy and safety testing. Moreover, such systems also limited the movement of the patient to a limited area near the vital signs monitor.
For example, an early telemetry system is described is U.S. Pat. No. 3,603,881 in which short transmission distances to a building""s wiring system are covered using VHF transmission. Physiologic data such as electrocardiographic (ECG) data is collected by a sensor and transmitted by a VHF transmitter to a fixed VHF receiver RF transmitter coupled to the wiring system in the building. An RF receiver demodulator monitor is coupled to the building""s wiring system at the nurse""s station for receiving the physiologic data for patient monitoring and/or data recording.
A similar telemetry system for monitoring ECTG signals is described in U.K. Patent Application No. 2 003 276 except that telephone connections are used in place of the building wiring and the system is also designed to collect blood pressure, pulse rate, respiratory rate and the like and to relate that information to the physician via the telephone connections.
Other early telemetry systems of the type described by Lewis in U.S. Pat. No. 3,943,918 and by Crovella et al. in U.S. Pat. No. 4,121,573 use telemetric techniques to transmit data from a sensor device attached to the patient""s chest via RF to a radio telemetry receiver for display and/or recording as desired. S.S. Ng described yet another telemetry system for ECG monitoring in an article entitled xe2x80x9cMicroprocesor-based Telemetry System for ECG Monitoring,xe2x80x9d IEEE/Ninth Annual Conference of the Engineering in Medicine and Biology Society, CH2513-0, pages 1492-93 (1987). Ng therein describes a system for providing continuous ECG monitoring and analysis by means of a PC AT via wireless link. In the Ng system, the patient requires a transmitter which is carried by the patient for sensing and transmitting the patient""s ECG signal to a central base station via wireless link. At the base station, a receiver recovers the original ECG signal from a few patients simultaneously for display.
Each of the above-described telemetry systems is designed primarily for hospital use and include relatively expensive sensor arrays and processing devices for real-time patient monitoring and diagnosis. The real-time monitoring is generally used in an xe2x80x9calarmxe2x80x9d mode to capture events, rather than to collect data over a period of time to determine trends which might indicate a more gradual deterioration or improvement in the patient""s condition or to predict a forthcoming event. Also, these systems require the patient to remain in close proximity to the base stations including the receivers.
Bornn et al. describe a portable physiological data monitoring/alert system in U.S. Pat. Nos. 4,784,162; 4,827,943; 5,214,939; 5,348,008; 5,353,793; and 5,564,429 in which one or more patients wear sensor harnesses including a microprocessor which detects potentially life-threatening events and automatically calls a central base station via radiotelemetry using a radio modem link. In a home or alternate site configuration, communications between the base station and remote unit is by way of commercial telephone lines. Generally, the system automatically calls xe2x80x9c911xe2x80x9d or a similar emergency response service when an abnormality is detected by the ECG monitor.
Unfortunately, the sensor harness is quite cumbersome and conspicuous and includes sensors for performing an alert function rather than data collection and analysis functions.
Segalowitz discloses a wireless vital signs monitoring system in U.S. Pat. Nos. 4,981,141; 5,168,874; 5,307,818; and 5,511,553 including a precordial strip patch including a multi-layer flexible structure for telemetering data by radio frequency or single wire to hardware recording apparatus and a display monitor. Microsensors and conductive contact elements (CCEs) are mounted on the strip patch so as to permit simultaneous and continuous detection, processing and transmission of 12-lead ECG, cardiac output, respiration rate, peripheral blood oximetry, temperature of the patient, and ECG fetal heart monitoring via a single wavelength of radio frequency transmission. While the precordial strip patch used by Segalowitz purportedly transmits vital signs data up to 50 meters, it requires a dual-stage operational amplifier chip, an encoder modulator chip, a wireless transmitter chip including an oscillator, and other costly components such as artificial intelligence software, sound and visual alarms, and a microprocessor. As a result, the precordial strip patch is relatively expensive to manufacture and operate. Also, as with the other telemetry systems noted above, the emphasis of Segalowitz is on real-time monitoring and alerting of medical personnel to immediate medical needs of the patient.
Platt et al. also disclose a sensor patch for wireless physiological monitoring of patients in U.S. Pat. No. 5,634,468. Platt et al. describe a sensor and system for monitoring ECG signals remotely from patients located in non-hospital sites. In this system, a sensor patch containing sensing electrodes, signal processing circuitry and radio or infra-red transmission circuitry is attached to the patient""s body and preferably worn for at least a week before its power supply is exhausted and the sensor patch is thrown away. A receiver at a primary site in the vicinity of the patient receives the data transmitted by the sensor patch and stores the sensed data. When the patient feels discomfort or concern, or if the portable unit sounds an alarm, the patient telephones the monitoring station and downloads the stored data from the portable unit via the standard voice telecommunications network. The downloaded ECG data is then monitored and analyzed at the monitoring station. The receiver in the proximity of the patient may be a portable unit carried around by the patient, where the portable unit includes a receiver, a processor for processing the received data to identify abnormalities, a memory for storing the sensed data, and circuitry for interfacing to a telephone line to send the ECG data signals to the monitoring station. The monitoring station decodes the received ECG signals and performs beat and rhythm analysis for classification of the ECG data. If an abnormal condition is discovered, medical personnel in the vicinity of the patient are contacted. While the system described by Platt et al. may collect ECG data from the patient and process it at a remote monitoring station, the data is only collected when the patient initiates the data download. Otherwise, data is lost once the memory in the portable unit is full. No mechanism is provided for continuously collecting data, at all times, in a way which requires no patient action.
In U.S. Pat. No. 5,522,396, Langer et al. disclose a telemetry system for monitoring the heart of a patient in which a patient station includes telemetering apparatus for transmitting the outputs of patient electrodes to a tele-link unit connected to a monitoring station by telephone lines. As in the Platt et al. system, Langer et al. transmit ECG data to a central location. However, unlike the Platt et al. system, the Langer et al. system checks the ECO data for predetermined events and automatically calls the monitoring station when such events are detected. A similar telemetry system is described by Davis et al. in U.S. Pat. No. 5,544,661 which initiates a cellular phone link from the patient to the central monitoring location when an event is detected. As with the Platt et al. system, neither of these systems provides a mechanism for continuously collecting data without patient action.
Accordingly, a telemetry system is desired which collects vital signs data from a patient using an inexpensive device which permits the continuous collection of a patient""s vital signs data without patient action. Also, a data management system is desired which permits the collected data to be reviewed and formatted for use in patient trials and the like. The present invention has been designed to meet these needs in the art.
The present invention meets the above-mentioned needs in the prior art by providing a portable remote patient telemonitoring system having four separate elements, each with different functions within the system.
The system of the invention is characterized by a first component, an adhesive, cordless, disposable sensor band with electrode patches, other sensors, and transmission circuitry for the detection and transmission of vital signs data. The sensor band is easy-to-use and is positioned on the patient by the patient. The sensor band is designed to be worn comfortably by the patient for 24 hours, at which time the sensor band may be discarded and replaced by a new sensor band.
The system of the invention is further characterized by a second component, a small signal transfer unit that can either be worn by the patient, e.g., on his or her belt, or positioned nearby (within approximately 1.5 meters), e.g., on a desk or chair or at the bedside. The function of the signal transfer unit is to receive data from the sensor band, which it then forwards by, e.g., radio transmission to a base station that can be located up to 60 meters away. The small signal transfer unit is designed to minimize the transmission requirements of the sensor band while also allowing the patient to move around freely while his or her vital signs are being monitored.
A third component, a base station, receives data transmissions from the signal transfer unit and is designed to connect to conventional phone lines for transferring the collected data to a remote monitoring station. The base station may also be designed to capture additional clinical data, such as blood pressure data, and to perform data checks. For data transfer, the base station connects the output of the sensor band, via modem and land or cellular telephone line, to the remote monitoring station. Connections for auxiliary sensors such as a blood pressure cuff extend the number of clinical parameters that can be captured. Patient safety is enhanced by the ability of the base station to compare clinical data, e.g. ECG, against given profiles and to raise alarms when appropriate or when the base station is programmed to do so. Such alarms could be indicated to the patient by reverse transmission to the signal transfer unit.
The fourth component, a remote monitoring station, allows the presentation and review of data (including event flags) forwarded by the sensor band and other sensors and simply requires a standard PC running, e.g., Windows NT. ECG analysis software and a user-friendly graphical user interface are provided to remotely analyze the transmitted data and to permit system maintenance and upkeep.
In preferred embodiments, the patient vital signs data collection and monitoring system of the invention is characterized by a sensor band having a sensor assembly for application to a patient. The sensor assembly produces a data signal including vital signs data indicative of values of at least one vital sign of the patient, and the sensor band further comprises a transmitter which transmits the data signal over a first communications link to a transceiver coupled to the first communications link so as to receive the vital signs data for retransmission of the data signal over a second, wireless communications link. A remote monitoring station is also provided which is disposed so as to receive the retransmitted data signal from the transmitter via the second communications link, where the remote monitoring station is characterized by its ability to capture the vital signs data for display and subsequent access and processing of the vital signs data for medical diagnosis or analysis.
In a preferred embodiment, the transceiver includes a buffer which stores vital signs data received from the sensor band at least during times when the second communications link is disconnected, lost, or unreliable. Also, the sensor band preferably comprises a transmitter having a first antenna which transmits the data signal over the first wireless communications link to a transceiver having a second antenna inductively coupled to the first communications link so as to form a wireless inductive loop with the first antenna for reception of the vital signs data. Also, in a preferred embodiment, the remote monitoring station captures the vital signs data and stores it in a database with vital signs data from a plurality of other patients. A user interface provides access to the vital signs data in the database for processing, medical diagnosis and/or analysis.
In presently preferred embodiments, the sensor band measures full waveform single or multiple lead ECG, full waveform respiration, skin temperature, and motion and transmits the measured data to the signal transfer unit, where the data is retransmitted to the base station. Auxiliary sensors may be provided at the base station including a blood pressure cuff, a spirometer, and weight scales. Also, the user interface at the remote monitoring station may contain full ECG analysis software covering waveform measurements, interval measurements, beat-typing and arrhythmia detection. xe2x80x9cEvent flagsxe2x80x9d also may be generated and indicated to the physician for high and low heart rate, high and low respiration rate, high and low temperature, high and low blood pressure or arrhythmias.
While there are many potential patient management applications for the remote telemetry system of the invention, such as remote measurement of cardiovascular abnormalities including hypertension, congestive heart failure, arrhythmia, silent ischaemia, and the like, and respiratory abnormalities including chronic obstructive pulmonary disease, in a presently preferred implementation of the invention, the remote telemetry system of the invention is also designed to reduce both the length and the cost of clinical drug trials by providing versatility in data collection with respect to site (in-clinic or domiciliary), time, and volume, and to provide direct, electronic data capture, which can be real-time if necessary. Additional applications include the monitoring of sleep apnea, diabetes, acute or sub-acute infection, asthma, and the like. The system of the invention may be used in a clinic or hospital setting but, when used in such settings, must be designed to minimize interference between radio signals.
Corresponding methods of collecting a patient""s vital signs data using the remote telemetry system of the invention are also described and claimed herein.